The present invention relates to a tilt detecting system and a tilt detecting method, by which a tilt of a photodetection device can be detected.
As a method for distance measurement to a measuring point, there is a method for measuring a distance to a measuring point, in which a target having retro-reflectivity is installed on a measuring point and a target is measured by a surveying instrument such as a total station.
Normally, a target is provided at an upper end of a pole and a lower end of the pole is installed at a measuring point. In order to accurately measure a distance to the measuring point, it is necessary for the target to be positioned just above the measuring point. In case the pole is tilted, it is necessary to detect a tilting angle of the pole and to correct the position of the target.
Conventionally, a laser plane is generated by rotary irradiation of a laser beam from a surveying instrument main unit along a reference line of a surveying instrument or a laser plane is generated by projecting a line laser expanding in a horizontal direction, and the laser beam is received by two detectors, which are separated from each other by a predetermined interval. Each detector has a length as required in a vertical direction. A deviation length between photodetecting positions of the two detectors with the laser plane as reference is measured and a tilting angle of the target with respect to the reference line of the surveying instrument is obtained from the interval and the deviation length of the two detectors.
In a case of the conventional method, it is so arranged that an accuracy of the tilting angle as detected is determined according to a resolving power of the measurement of the interval and the deviation length between two detectors, and the interval between the two detectors must be increased in order to improve the detection accuracy. On the other hand, a measurement range of the tilting angle is determined according to the interval between the two detectors and the size (i.e. size of a photodetecting range) of the two detectors. In order to keep the measurement range as desired, there has been a problem in that the size of the detectors must be increased in proportion to the interval between the two detectors.
Further, conventionally, detecting of a tilting angle with respect to horizontal and vertical lines are possible, but cannot be attained with a high accuracy and a high responding speed, and there has been no tilt detecting device, by which a tilt of a target separated from the reference line of a surveying instrument main unit can be measured at higher speed and at higher accuracy and which can be miniaturized.